Release/anti-preset mechanism for down-hole tools

ABSTRACT

This invention relates to a release/anti-preset mechanism for retrieving a down-hole tool and for preventing premature actuation of the tool during insertion thereof into a subterranean well-bore. Release mechanisms for retrieving down-hole tools are known and can be divided into three main types: shear release systems, conventional wireline/coil tubing/drill pipe (WL, CT, DP) actuated systems and hydraulically activated systems. Known mechanisms suffer from a number of problems. Accordingly the present invention provides a retrievable down-hole tool (5) having a release/anti-preset mechanism comprising first and second members (10, 15) radially releasably engagable by a third member (20) which controls radial deflection of one of the first or second members (10, 15).

BACKGROUND OF THE INVENTION

This invention relates to a release mechanism for retrieving down-holetools, and in particular, though not exclusively, to a packerincorporating such a releasing mechanism. This invention also relates toa (non-hydraulic) anti-preset mechanism which prevents prematureactuation of a down-hole tool during insertion thereof into asubterranean well-bore.

PRIOR ART

Release mechanisms for retrieving down-hole tools are known and can bedivided into three main types: shear release systems, conventionalwireline/coil tubing/drill pipe (WL, CT, DP) actuated systems andhydraulically activated systems.

In shear release systems members are retained in a locked position byuse of a shear or tension member(s) positioned between them. Appliedforces less than the shear value may be accommodated without actuatingthe device. If, however, the shear value is exceeded the shear memberfails permitting relative movement and release. One limitation to thissystem is that the shear value for practical purposes must be setrelatively low in order to ensure that it will fail before componentstransmitting the lead exceed their operating capacity. For example, whenpulling a shear release packer, the top joint in the production tubingis subject to the buoyant weight of the string in addition to appliedtension, whereas the shear member placed at the bottom of the string mayonly be subject to applied tension less frictional losses of the tubingstring within the casing string. Conversely, it may be necessary to setthe shear value relatively high in order to ensure that the stresseswithin the shear member are kept below an acceptable level in order toensure that the shear member does not fail under all anticipatedoperating conditions. In many cases these two competing requirementsoverlap and in these cases such a system is not viable. Anotherdisadvantage is that accurate assessments of frictional drag ofproduction tubing are not normally possible. An example of a shearrelease system for a packer is the Applicants own packer Product Ref:722 HR.

In conventional WL/CT/DP actuated systems either collets or dogs havebeen used which permit the system to be loaded to values greater thanthe design limits of the tubing string prior to actuation. Dogs may beplaced in a position between load bearing flanks of two relevant parts.The dogs are held radially in place by a support sleeve. When axialloads are applied the dog transmits the loads from one load flank to theother. The support sleeve absorbs the relatively small radialcompressive forces due to the radial component of the flank angle(threads) in the outer member but is not subject to any axial loadingdue to applied-tubing loads. The support sleeve is held in place by ashear device. To activate the system, it is necessary to apply anindependent axial load against the support sleeve to shear the screwsand cause relative movement to a position in which the dogs are nolonger constrained radially to engage the load flank on the externalmember. This external load can be applied by dedicated devices conveyedinto the well on wireline, coiled tubing or on drill pipe. Collet basedsystems are similar to dog based systems except that the collet can beproduced as an integral part of one of the members.

A disadvantage of both these systems is that it is necessary to provideseals to close off communication either through the dog windows orthrough the collet gaps in order to attain tubing to annular integrity.Also, although various means are usually employed to minimize thepotential that wireline or coiled tubing operations will not cause thesupporting sleeve to shear (high shear values, selective profiles,recessed diameters) the possibility of inadvertent release cannot betotally excluded.

Examples of a collet based release system can be found in most gravelpack seal bore packers. An example of a dog based system is theApplicants own Product Ref: AV1 CAPS.

In hydraulically activated systems a supporting member to the dog orcollet is in some manner attached to or part of a piston which moves inresponse to exceeding a defined pressure differential. The piston couldbe placed between tubing and annulus and activated by differentialpressure between the two. Examples include the Baker Iso-pak settingsystem disclosed in U.S. Pat. No. 4,936,387 and the Brown HB-S releasesystem.

In such systems the piston seals present a potential leak path.Providing an atmospheric chamber is an option which eliminates the issueof compromising tubing to annulus integrity but also limits thepractical life of the mechanism so such atmospheric systems are usuallyused for actions during installation (setting) rather than operationsoccurring after a long time such as releasing. Examples include theBaker FH and A5 packer setting systems.

In order to deal with the need to operate at higher differentials thanthe actuating pressure, in other words to permit selectivity, pressureaccess to the release piston can be isolated in various ways.Traditionally a wireline/coiled tubing activated sleeve is used. Thisoption adds redundancy but does not eliminate the potential leak pathand of course introduces possible inadvertent actuation duringwireline/coiled tubing operations. An example of this type of system isthe selective setting feature of the Baker FH packer. Recently the useof a tubing punch to perforate a continuous member has been used whichaddresses these weaknesses but requires complex systems and operationsto activate the device. An example of this system is the release systemof the Applicants own Product Ref: AV2 CAPS.

Often hydraulically activated anti-preset mechanisms are incorporatedinto hydraulically set down-hole tools to improve reliability duringinsertion of the tool into the well-bore. Packers are set by permittingconcentric components to slide axially to expand slips and packingelements during insertion, such movement is undesirable and would betermed "presetting" the packer. In conventional anti-preset mechanisms ashifting piston is used to constrain a dog, collet, or C-ring so that anadjacent piston cannot move and is effectively locked to the mandrel.During tool insertion, the outer components are locked to the mandrel bythe hydraulic anti-preset mechanism. Application of tubing pressurecauses a shear pin in the shifting piston to shear, allowing movement ofshifting piston to unlock the adjacent piston. The adjacent piston isnow free, additional hydraulic pressure causing the piston to stroke andset the packer. This mechanism is known from Baker FH, Hydra-pak, andIso-pak packers.

OBJECTS OF THE INVENTION

It is an object of the present invention to obviate or mitigate at leastsome of the aforementioned problems/disadvantages of the prior art.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided aretrievable down-hole device having a release/anti-preset mechanismcomprising first and second members radially releasably engagable by athird member which controls radial deflection of one of the first orsecond members.

Preferably the first and second members are substantially cylindrical incross-section, the first member being of smaller diameter than thesecond member.

In this case the third member may be located within the first member soas to control radial deflection thereof.

Engagement of the first and second members may be provided betweenco-acting recessed/proud portions on a radially outer surface of thefirst member and a radially inner surface of the second member.

The co-acting recessed/proud portions may be in the form of respectivefirst and second threaded portions.

The third member may be a C-ring having a prepared slot capable ofreceiving a tapered pin.

The C-ring may be in the form of two concentric C-rings suitably heldtogether.

Alternatively, the third member may be: a sleeve with recesses, acylinder fabricated from shape memory alloy, a cylinder with a thermalinsulator on the exterior, or any of a range of systems that could bemanipulated into a shape With an effectively reduced outer diameter.

Preferably at least one of the first or second members defines asinternal to external pressure barrier.

The retrievable down-hole device may be a packer.

According to a second aspect of the present invention there is provideda method of retrieving a retrievable down-hole device comprising thesteps of:

providing the device with a release/anti-preset mechanism comprisingfirst and second members radially releasably engaged by a third memberwhich controls radial deflection of one of the first or second members;and

controlling the third member so as to radially release the first andsecond members from one another thereby allowing retrieval of the tool.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described, by way ofexample only, with reference to the accompanying drawings, which are:

FIGS. 1(A), (B), (C) a side view in partial cross-section of aretrievable isolation packer including a release/anti-preset mechanismaccording to one embodiment of the present invention;

FIG. 2 a cross-sectional end view of the packer of FIG. 1 taken alongline A--A;

FIG. 3 a cross-sectional end view of the packer of FIG. 1 taken alongline B--B;

FIG. 4 a perspective view of a C-ring and tapered pin used in the packerof FIG. 1;

FIG. 5 a partial cross-sectional view of the packer of FIG. 1 rotatedthrough 90°;

FIG. 6 a partial cross-sectional view of the packer of FIG. 1 to anenlarged scale.

DETAILED DESCRIPTION OF AN EMBODIMENT

Referring now to the figures there is illustrated a retrievabledown-hole tool in the form of a retrievable isolation packer, generallydesignated 5, having a release/anti-preset mechanism according to oneembodiment of the present invention.

The release/anti-preset mechanism comprises a first member in the formof a main body or mandrel 10 and a second member in the form of a lowercone 15. The main mandrel 10 and lower cone 15 are radially releasablyengagable with one another by means of a third member in the form of aC-ring 20 which controls radial deflection of the main mandrel 10.

Engagement of the main mandrel 10 and lower cone 15 is provided by meansof co-acting first and second threaded portions 25, 30 on a radiallyouter surface of the mandrel 10 and a radially inner surface of thelower cone 15.

The C-ring 20 which has a tapered slot 35 is positioned within an innerdiameter of the main mandrel 10. A tapered pin 40 can be inserted in theslot 35 so that axial movement of the pin 40 toward the C-ring 20 causestapered surfaces of the slot 35 to move apart expanding the outer andinner diameters of the C-ring 20. Further axial movement of the pin 40towards the C-ring 20 causes the C-ring to radially load the innerdiameter of the mandrel 10.

Further similar movement causes the inner and outer diameters of themandrel 10 to elastically deflect radially outward. The first threadedportion 25 is machined on the outer diameter of the mandrel 10, radialof the C-ring 20. Insertion of the tapered pin 40 causes the firstthreaded portion 25 to engage with the second threaded portion 30. Thus,once the pin 40 is inserted into the slot 35 the lower cone 15 is lockedto the mandrel 10. In the above described position of the releasingmechanism, the packer 5 is run downhole.

As can be seen from FIG. 4 the tapered pin 40 is integrally formed withan annular ring 45 which ring 45 has on an inner surface a shiftingprofile 50 similar to releasing (or shifting) sleeves on existingproducts. When a shifting tool is run in to the shifting profile the pin40 can be pulled from the C-ring 20; the C-ring 20 thereby reduces indiameter, the mandrel 10 elastically retracts and the co-acting threadedportions 25, 30 disengage. The lower cone 15 is then free to moveseparate from the mandrel 10. Pulling of the packer 5 will cause thelower cone 15 to move thereby releasing the tool. As can be seen fromFIG. 1(C) the annular ring 45 is, in this embodiment, shear pinned tothe main mandrel 10 by shear screws 46. A preset upward jarring forcemust, therefore, be applied to the ring 45 by the shifting tool to shearthe shear screws 46 thereby allowing retraction of the pin 40.

The above describes the release mechanism per se. A description will nowbe given of the packer 5 and the operation thereof.

The packer 5 is provided at an uppermost end with a threaded connectorsub 55 suitable for connecting the packer 5 to drill string. The sub 55is connected to a first end of the main mandrel 10. The packer 5 isfurther provided at a lowermost/innermost end with a further threadedconnector sub 60 suitable for connecting the packer 5 to drill string.The further sub 60 is connected to a second end of the main mandrel 10.

A retainer ring 65 is provided near the outermost end of the mainmandrel 10, which retainer ring 65 is connected thereto by threads orthe like. Abutting an innermost surface of the ring 65 is an end of acylinder 70.

The cylinder 70 provides with the mandrel 10 a cylinder chamber 75containing a first piston 80 and a second piston 85 containing dogs 90.The pistons 80, 85 are sealed by O-rings 95. An upper stop ring 100 isprovided and the cylinder 70 has a plurality of ports 105.

On a radially inner surface of the cylinder 70 at or near a lowermostend thereof there is provided a body lock ring 110. Further betweenradially inner and outer surfaces of the second piston 85 and mandrel 10there is provided an anti rotation key 111. A lowermost/innermost end ofthe cylinder is sheer screwed to an upper gauge ring 115 by sheer screws120. A lowermost/innermost surface of the upper gauge ring abuts anuppermost/outermost facing surface of a packing element 125. The packingelement 125 comprises an end element 130, a centre element 135 and afurther end element 140 spaced by element spacers 145, alowermost/innermost facing surface of a packing element abuts a lowerelement insert ring 150 which is sheer screwed to an upper cone 155 bysheer screws 160. The upper cone 155 provides a plurality of lower dogsegments 165. Further, on an outermost surface of the lower elementinsert ring 150 there is provided a lower gauge ring 170.

The upper cone 155 is sheer screwed by screw 171 to a key 175 adjacentto a plurality of slips 180 maintained in position by a slip retainerring 185 fixed by sheer screws 190. The lower cone 15 contacts anlowermost end of the slips 180. Upward movement of the lowermost cone 15is restricted by a lower stop ring 195 provided on an outermost surfaceof the mandrel 10.

A bypass line 196 runs along the length of the tool 5 which line may beused to hydraulically control further tools downline of the tool 5.

As can be seen from FIG. 5 the tool 5 may be controlled by means of asetting control line 200, which communicates with an uppermost end ofthe second piston 85.

An inner sleeve 205 is provided within the main mandrel 10 at an endadjacent sub 60, the sleeve 205 restricting downward movement of theC-ring 20.

Operation of the tool 5 will now be described. Prior to lowering thetool 5 down-hole, the pin 40 is located in the tapered slot 35 of theC-ring 20, thereby elastically loading the C-ring 20 and the mainmandrel 10 so as to connect the main mandrel 10 and the lower cone 15via the co-acting threaded portions 25, 30. Once the tool 5 has beenlowed downhole to the required position, the slips 180 and packingelement 125 may be set as follows. Pressure may be applied via thesetting control line 200 thereby causing upward movement of the firstpiston 80. Upon such movement of the first piston 80, the upper dogsegments 90 may extend radially outwards thereby allowing downwardmovement of the second piston 85. Such movement of the second piston 85causes shear screws 120 to shear provided the applied pressure is abovea pre-determined threshold pressure. Shearing of the shear screws 120causes downward movement of the upper gauge ring 115 thereby loading thepacking element 125. Loading of the packing element 125 consequentlycauses shear screws 160 to shear and downward movement of the elementinsert ring 150. Such movement of the insert ring 150 allows the lowerdog elements 165 to extend radially outwards thereby allowing downwardmovement of the upper cone 155 and key 175. Such movement causesshearing of shear screws 190 and thereby outward setting of the slips180. As further force is applied downward shear screws shear causing theupper cone 155 to move free of the key 175 and finalise the setting ofthe slips 180.

Retrieval of the tool 5 is carried out as follows. A retrieval tool maybe lowered so as to grasp the shifting profile 50 within the annularring 45. Pulling of the setting tool in such position above the presetforce shears screws 46 thereby allowing release of the pin 40 from thetapered slot 35. Consequently the diameter of the C-ring 20 reduces andelastic extension of the mandrel 10 is removed. Consequently thethreaded portions 25, 30 of the lower cone 15 and mandrel 10 releasefrom one another, and the lower cone 15 is allowed to fall away from themandrel 10. Pulling on the packer 5 causes the mandrel 10 to move upwardrelative to the casing string. As the mandrel 10 is moving upward, theslips 180, and ring 185, will pick up on the lower stop ring 195 thuspreventing lower ends of the slips 180 from re-engaging the lower cone15 during retrieval. Further movement upward of the mandrel 10 causesthe lower end of the key 175 to shoulder out in a slot 191, then theupper cone 155 to shoulder out in cone slot 156. This prevents the uppercone 155 from re-engaging the upper end of the slips 180 duringretrieval. Further movement upward of the mandrel 10 causes the packingelement 125 to relax and move downward while the second piston 85strokes down and shoulders against the upper end of the body lock ring110. In this way the tool 5 may be retrieved.

The embodiment of the invention hereinbefore described is given by wayof example only and is not meant to limit the scope of the invention inany way. Various modifications of the disclosed embodiment maytherefore, be envisaged by the skilled person without departing from thescope of the invention.

Particularly a modification to the C-ring may be that the C-ring can beprovided by two separate C-rings. These separate C-rings would bemachined with a slight interference then slotted and assembledconcentrically, Once they are assembled they will act as a single memberand can collectively be called a single C-ring.

Finally, it should be appreciated that the terms upward, downward,outermost and innermost should be construed in a common sense way withrespect to a subterranean well bore per se, these terms being used forsimplicity of description and not to limit the orientation of use of thetool in any way.

What is claimed is:
 1. A retrievable downhole tool having arelease/anti-preset mechanism, comprising:first and second membersradially releasably engageable by a third member which controls radialdeflection of one of said first or second members, wherein said firstand second members are substantially cylindrical in cross-section andsaid first member has a smaller diameter than said second member, andwherein engagement of said first and second members is provided betweenco-acting recessed portions on a radially outer surface of said firstmember and a radially inner surface of said second member.
 2. Aretrievable downhole tool as recited in claim 1, wherein said thirdmember is located within said first member so as to control radialdeflection thereof.
 3. A retrievable downhole tool as recited in claim4, wherein said co-acting recessed portions are in the form ofrespective first and second threaded portions.
 4. A retrievable downholetool as recited in claim 3, wherein said C-ring is in the form of twoconcentric C-rings suitably held together.
 5. A retrievable downholetool as recited in claim 1, wherein at least one of said first or secondmembers defines an internal to external pressure barrier.
 6. Aretrievable downhole tool as recited in claim 1, wherein saidretrievable downhole tool comprises a packer.
 7. A retrievable downholetool having a release/anti-preset mechanism, comprising:first and secondmembers radially releasably engageable by a third member which controlsradial deflection of one of said first or second members, wherein saidthird member is a c-ring having a tapered slot capable of receiving atapered pin.
 8. A retrievable downhole tool having a release/anti-presetmechanism, comprising:first and second members radially releasablyengagable by a third member which controls radial deflection of one ofsaid first or second members, wherein said third member comprises acylinder fabricated from a shape memory alloy.
 9. A retrievable downholetool having a release/anti-preset mechanism, comprising:first and secondmembers radially releasably engagable by a third member which controlsradial deflection of one of said first or second members, wherein saidthird member comprises a cylinder having a thermal insulator on theexterior of said cylinder.